Original article In vivo molecular imaging of HER2 expression in a rat model of Barrett’s esophagus adenocarcinoma S. Realdon, 1,2 * E. Dassie, 1,2 * M. Fassan, 3 L. Dall’Olmo, 1 G. Hatem, 4 A. Buda, 4 D. Arcidiacono, 1,2 G. Diamantis, 1 H. Zhang, 5 M. I. Greene, 5 G. C. Sturniolo, 4 M. Rugge, 3 A. Alberti, 2,6 G. Battaglia 1,4 1 Endoscopy Unit, Istituto Oncologico Veneto – IOV-IRCCS, 2 Venetian Institute of Molecular Medicine (VIMM), 3 Department of Medicine (DIMED), Surgical Pathology and Cytopathology Unit, 4 Department of Surgical Oncology and Gastroenterology Sciences (DiSCOG), Gastroenterology Unit, 6 Department of Molecular Medicine, University of Padua, Padua, Italy; and 5 Department of Pathology and Lab Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA SUMMARY. Human epidermal growth factor receptor 2 (HER2) is involved in the malignant progression of several human cancers, including esophageal adenocarcinoma (EAC). The purpose of this study was to evaluate HER2 overexpression and to explore the feasibility of confocal laser endomicroscopy for in vivo molecular imaging of HER2 status in an animal model of Barrett’s-related EAC. Rats underwent esophagojejunostomy with gastric preservation. At 30 weeks post-surgery, the esophagus of 46 rats was studied; endoscopic and histological findings were correlated with HER2 immunofluorescence on excised biopsies and gross specimens. At this age, 23/46 rats developed Barrett’s esophagus (BE), and 6/46 had cancer (four EAC and two squamous cell carcinomas). A significant overexpression of HER2 was observed in esophageal adenocarcinoma compared with normal squamous esophagus (9.4-fold) and BE (6.0-fold). AKT and its phosphorylated form were also overexpressed in cancer areas. Molecular imaging was performed at 80 weeks post-surgery in four rats after tail injection of fluorescent-labeled anti-HER2 antibody. At this age, 3/4 rats developed advance adenocarcinoma and showed in vivo overexpression of HER2 by molecular confocal laser endomicroscopy with heterogeneous distribution within cancer; no HER2 signal was observed in normal or Barrett’s tissues. Therefore, HER2 overexpression is a typical feature of the surgical induced model of EAC that can be easily quantified in vivo using an innovative mini-invasive approach including confocal endomicroscopy; this approach may avoid limits of histological evaluation of HER2 status on ‘blinded’ biopsies. KEY WORDS: Barrett’s esophagus, confocal laser endomicroscopy, esophageal adenocarcinoma, human epider- mal growth factor receptor 2, molecular imaging. ABBREVATIONS: BE, Barrett’s esophagus; CLE, confocal laser endomicroscopy; EAC, esophageal adenocarcinoma; GEJ, gastroesophageal junction; HER2, human epidermal growth factor receptor 2; ROI, region of interest; SCC, squamous cell carcinoma; SEM, standard error of the mean; WLE, white-light endoscopy. INTRODUCTION Esophageal adenocarcinoma (EAC) is the sixth leading cause of cancer-related deaths in the industri- alized world. 1 Barrett’s esophagus (BE) is the major precursor of EAC occurring in the distal esophagus, and BE patients have 40-folds increased life risk of developing esophageal cancer. 2,3 Despite important recent advances in early detection and treatment, its prognosis remains poor. 4–7 Address correspondence to: Professor Alfredo Alberti, MD, Department of Molecular Medicine, Via Gabelli 9, 35121 Padua, Italy. Tel. (+39) 0498212293; Fax: (+39) 0498211826; Email: alfredo.alberti@unipd.it *SR and ED contributed equally to this work. Author contribution: SR, ED: study design, data acquisition, manuscript preparation; LD: surgery; MF, MR: histology; GH, AB, DA, GD, GCS, HZ, MIG: data interpretation; AA, GB: study supervision, obtained funding. Grant support: This work was supported by AIRC (Italian Association for Cancer Research, project n. 10761). The funding agency had no role in the design and conduct of the study. Conflicts of interest: The authors disclose no conflicts. Diseases of the Esophagus (2014) ••, ••–•• DOI: 10.1111/dote.12210 © 2014 International Society for Diseases of the Esophagus 1